Vehicle configuration

The decision to fly a two-orbit rather than a three-day mission allowed the Russians to significantly reduce the number of on-board systems and thereby move up the launch date. Apart from requiring less sophisticated software, the shorter flight obviated the need for installing such systems as fuel cells, a payload bay door opening mechanism, payload bay door radiators, etc. The only objective of the flight was to see if Buran could safely reach orbit and return back to Earth. With no crew on board, few of the life support systems needed to support humans were carried. For instance, Buran had a 90 percent nitrogen/10 percent oxygen atmosphere to minimize the risk of fire.

Original plans called for the space-rated orbiters to be equipped with two Lyulka AL-31 turbojet engines to provide flight path modification capability during the return to Earth. For this purpose Buran had two niches on either side of the vertical stabilizer to house the engine pods. However, in late 1987/early 1988 a decision was made not to install the engines, fill the niches with panels, and cover them with ATM-19PKP flexible thermal insulation.

There is conflicting information on the reasons for this decision. One source claims the atmospheric landing tests performed with the full-scale BTS-002 vehicle had shown that control was sufficient without these engines [32]. Another says the engines were not ready for the first flight. Although they had been flown on the BTS – 002, they had never been ignited in flight, nor had the thermal protection covers for the engine inlet and outlet been tested. On top of that, there were mass-related issues that needed to be addressed before the engines were flown. Not only did the engines weigh about 400 kg each, they also required support systems such as a kerosene tank (probably to be placed in the mid fuselage under the payload bay), fire suppression systems, etc. However, once those issues had been resolved, the engines might well have flown on future missions [33]. One may also speculate that the presence of the engines would have unnecessarily complicated the automatic flight program for the maiden mission. Interestingly, the throttle lever for the AL-31 engines was not removed from Buran’s cockpit for the first flight. The removal of the AL-31 engines slightly changed the vehicle’s center of gravity and placed higher aerodynamic loads

on the vertical stabilizer. Therefore, additional wind tunnel tests were run to make sure that the absence of the engines posed no unexpected problems.

Buran’s cargo bay was not empty during the first flight. Sitting in the middle of the cargo bay was a pressurized module known as Unit for Additional Instruments (BDP for Blok Dopolnitelnykh Priborov) or 37KB. BDP performed a role similar to

the Development Flight Instrumentation (DFI) on the orbital test flights of the US Space Shuttle. It was stowed full with instrumentation to record about 6,000 param­eters during the flight and also carried support equipment such as batteries to compensate for the absence of fuel cells on Buran’s maiden mission.

Its design was based on a series of modules (37K) originally planned for the Mir space station, only one of which (Kvant or 37KE) was eventually flown. On 19 April 1982 the KB Salyut design bureau (then a branch of NPO Energiya) received an order to develop a series of such modules for Buran that would carry out a variety of functions. Built at the Khrunichev factory, the first such module (serial nr. 37070) was shipped to Baykonur in February 1986 to be flown on the maiden mission of Buran. After having been tested in the Proton area of the cosmodrome, it was transported to the MIK OK orbiter-processing facility for installation into Buran. Weighing 7,150kg, it was 4.1m wide, 5.1m long, and had an internal volume of 37m3. The ultimate plan was to turn these modules into small scientific laboratories that could either remain in the cargo bay of Buran (like Spacelab) or be temporarily attached to space stations (see Chapter 8) [34].